Merge pull request #299 from dotty-staging/try-handling

Try handling inside patternmatcher

Author: DarkDimius

src/dotty/tools/dotc/printing/RefinedPrinter.scala

@@ -468,7 +468,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
     if (tree.isEmpty) "" else encl(toText(tree))
 
   def optText[T >: Untyped](tree: List[Tree[T]])(encl: Text => Text): Text =
-    if (tree.exists(!_.isEmpty)) "" else encl(blockText(tree))
+    if (tree.exists(!_.isEmpty)) encl(blockText(tree)) else ""
 
   override protected def polyParamName(name: TypeName): TypeName =
     name.unexpandedName()

src/dotty/tools/dotc/transform/PatternMatcher.scala

@@ -9,7 +9,7 @@ import core.Symbols._
 import core.Types._
 import core.Constants._
 import core.StdNames._
-import dotty.tools.dotc.ast.{TreeTypeMap, tpd}
+import dotty.tools.dotc.ast.{untpd, TreeTypeMap, tpd}
 import dotty.tools.dotc.core
 import dotty.tools.dotc.core.DenotTransformers.DenotTransformer
 import dotty.tools.dotc.core.Phases.Phase
@@ -52,6 +52,19 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {thisTrans
     translated.ensureConforms(tree.tpe)
   }
 
+
+  override def transformTry(tree: tpd.Try)(implicit ctx: Context, info: TransformerInfo): tpd.Tree = {
+    val selector =
+      ctx.newSymbol(ctx.owner, ctx.freshName("ex").toTermName, Flags.Synthetic, defn.ThrowableType, coord = tree.pos)
+    val sel = Ident(selector.termRef).withPos(tree.pos)
+    val rethrow = tpd.CaseDef(sel, EmptyTree, Throw(ref(selector)))
+    val newCases = tpd.CaseDef(
+      Bind(selector,untpd.Ident(nme.WILDCARD).withPos(tree.pos).withType(selector.info)),
+      EmptyTree,
+      transformMatch(tpd.Match(sel, tree.cases ::: rethrow :: Nil)))
+    cpy.Try(tree)(tree.expr, newCases :: Nil, tree.finalizer)
+  }
+
   class Translator(implicit ctx: Context) {
 
   def translator = {